1. Field of the Invention
This invention relates generally to lithography, and, more particularly, to soft lithography.
2. Description of the Related Art
Soft lithography is a patterning technique used in micro-fabrication to produce microstructures by transferring a pattern from a master to a substrate using a patterned elastomer. For example, patterns may be transferred by printing, molding, or embossing with a polydimethylsiloxane (PDMS) elastomeric stamp. The elastomeric stamp can be prepared by casting prepolymers against masters patterned by conventional photolithographic techniques. Representative soft lithographic techniques include contact printing, replica molding, transfer molding, micro-molding in capillaries, solvent assisted micro-molding, and the like. These soft lithographic techniques may be useful for fabricating a variety of functional components and devices that may be used in areas including optics, microelectronics, microanalysis, micro-electro-mechanical systems, and the like.
Decal transfer lithography is a type of soft lithography based on the transfer of polydimethylsiloxane patterns to a substrate via the engineered adhesion and release properties of a compliant polydimethylsiloxane stamp. FIGS. 1A, 1B, 1C, and 1D conceptually illustrate a conventional decal transfer lithography technique. FIG. 1A shows a silicon-containing elastomer 10 that has been patterned using a master pattern 20. The silicon-containing elastomer 10 is then removed from the master pattern 20, as shown in FIG. 1B, and placed in contact with a substrate 30 such that the portions of the silicon-containing elastomer 10 that are in contact with the substrate 30 become irreversibly attached to the substrate 30. A bulk portion 40 of the silicon-containing elastomer 10 is pulled away from the substrate 30. The silicon-containing elastomer 10 undergoes cohesive failure, leaving behind a patterned portion 50 of the silicon-containing elastomer 10.
Conventional decal transfer techniques, such as the technique shown in FIGS. 1A-D, are useful for delivering micron-size polydimethylsiloxane patterns to flat or curved large-area electronic materials such as silicon, silicon dioxide, and other metals in films. However, conventional decal transfer techniques may not be able to effectively transfer submicron-size patterns due to limitations arising from the mechanical properties of the polymers used to form the elastomeric stamps. For example, the locus of cohesive failure of the silicon-containing elastomer 10 shown in FIGS. 1A-D progressively approaches a surface of the patterned features 50 as the size of the patterned features 50 approach the 1 micron level.
The present invention is directed to addressing the effects of one or more of the problems set forth above.